Note: Descriptions are shown in the official language in which they were submitted.
CA 02222820 1997-11-28
STRESS PLATE WITH ANGLED HOLE
BACKGROUND OF THE INVENTION
The present invention relates generally to fastening systems for. use in
securing relatively soft insulation to a solid base, and specifically, to
stress plates and
associated threaded fasteners used for securing insulation and membranes to a
building
S structure.
In certain modern roofing installations of commercial and factory buildings
having a flat roof design, a layer of insulation is placed on a generally
corrugated steel
roof deck, and is then covered with a single ply thermoplastic roofing
membrane to
protect against the elements. Conventional membranes are single ply and are
made of
plastics such as EPDM, PVC or equivalent materials.
The assemblies typically used to secure the insulation generally include a
washer-like stress plate made of either plastic or metal which receives a
screw-like
fastener that is threaded into the roof deck, clamping the insulation between
the stress
CA 02222820 1997-11-28
plate and the roof deck. Since the type of insulation commonly utilized is
approximately
up to six or even twelve inches thick, it is important to keep the fastener in
perpendicular
alignment when installing the plate so that the stress plate ,properly
contacts and secures
the insulation against blowing off from extreme cyclical loading. Adverse
weather
S conditions such as hurricanes and other storms having high and gusting winds
create the
extreme high pressure dynamic loading, including uplift, of the sort which
such roofing
is designed to withstand. In practice, special tools may be used to install
the washers and
fasteners. An example of such a tool is described in U.S. Patent No.
4,809,568, and
another such tool is sold by ITW Buildex, Itasca Illinois under the mark
ACCUFAST.
In a typical installation, the stress plates and fasteners are delivered to
the
jobsite in separate packages. Next, the installer obtains a supply of plates
and fasteners,
and lays out the plates on the roof in a specific pattern required by the
roofing approval
or warranty. Upon completion of that step, the installer installs fasteners
through the
plates, into the insulation and/or membrane, and eventually into the solid
roof base or
substrate.
A disadvantage of this method of installation is that it requires the
installer
to spend a significant amount of time to perform the two major steps of
separately
handling the stress plates and the fasteners. Also, once installed, the
alignment of the
fasteners relative to the plates and the roof must be maintained under
relatively exposed
working conditions. Often it is difficult to prevent the fasteners from being
threaded into
2
CA 02222820 1999-12-24
the roof at an angle, which may detract from their ability to secure the roof
when
exposed to severe weather.
Thus, the present invention seeks to provide an improved stress plate which
is specially designed to hold the fastener at a perpendicular orientation to
the roof
while it is being installed.
Further, the present invention seeks to provide an improved stress plate in
which an opening or hole in the plate is oriented at an angle which
corresponds to
the helix angle of the threads of the fastener used to secure it to the roof.
Still further, the present invention seeks to provide an improved fastener
assembly for use in securing relatively soft materials to a solid base, such
assembly
including a stress plate and a fastener preinstalled into the plate and held
relative
thereto at a perpendicular angle to facilitate proper installation.
SUMMARY OF THE INVENTION
The above-identified objects are met or exceeded by the present stress plate
for use with a threaded fastener in attaching a roofing membrane to a roof. A
major feature of the stress plate is that the hole which accommodates the
fastener
is configured to retain the fastener in a perpendicular orientation to the
plate, and
ultimately, to the roof. In the preferred embodiment, the threads of the
fastener
have a helix angle, and the hole is angled at the same angle as the threads of
the
fastener to maintain this perpendicular orientation. In addition, the present
plate
is preferably provided to the installer as an assembly with the fastener
threaded
into the hole in the plate.
More specifically, a stress plate for use with a threaded fastener for
securing
3
CA 02222820 1999-12-24
relatively soft insulation to a solid base, such as in a roofing environment,
includes
a generally planar main body, and a hole on said main body configured for
receiving
the fastener. The plate is configured so that the hole is angled relative to a
vertical
axis of the plate for accommodating threads of the fastener so that the
fastener is
maintained in a generally perpendicular orientation to the main body upon the
engagement of the threads of the fastener in the hole.
Accordingly, the invention in one aspect provides a stress plate for use with
a threaded fastener for securing relatively soft insulation to a solid base,
comprising
a generally planar main body with a hole on the main body configured for
receiving
the fastener, the hole being defined by a depression generally centrally
formed in
the main body. In defining the hole, the depression has a first side and a
second
side, the second side being shorter than the first side.. The hole has first
and
second side walls, each located between the first and second sides. The
fastener
has a root diameter and the thread has an outer diameter wherein the first
side wall
engages the root diameter and the second side wall engages the outer diameter.
The hole is configured to be planar and angled relative to a vertical axis of
the plate
for accommodating threads of the fastener, the planar configuration and the
engagement of the side walls with the fastener being such that the fastener is
maintained in a generally perpendicular orientation to the main body upon the
engagement of the threads of the fastener in the hole.
In another aspect, the invention comprehends a fastener assembly for
securing relatively soft insulation to a solid base, comprising a fastener
having a
head, a tip and a threaded portion located between the tip and the head, a
stress
plate having a generally planar main body with a generally central hole on the
main
4
CA 02222820 1999-12-24
body configured for receiving the fastener. The hole is defined by a
depression
generally centrally formed in the main body and in defining the hole, the
depression
has a first side and a second side, the second side being shorter than the
first side.
The hole has first and second side walls, each located between the first and
second
sides. The fastener has a root diameter and the thread has an outer diameter
wherein the first side wall engages the root diameter and the second side wall
engages the outer diameter. At least one strengthening corrugation is formed
in
the plate to surround the depression and the plate is configured so that the
hole is
planar, yet angled relative to a 'vertical axis of the plate for accommodating
the
threaded portion of the fastener so that the fastener is maintained in a
generally
perpendicular orientation to the main body upon the engagement of the threaded
portion of the fastener in the hole.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overhead plan view of the present stress plate having a fastener
engaged therein;
FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1 and in the
direction indicated generally;
FIG. 3~is a view of the stress plate as depicted in FIG. 2 with the fastener
omitted;
FIG. 4 is an exploded schematic representation of the process of fabricating
the stress plate of FIG. 3;
FIG. 5 is a fragmentary enlarged elevational view of the fastener shown in
FIG. 2;
4a
CA 02222820 1997-11-28
FIG. 6 is a side elevational view of the portion of the present stress plate
depicted in FIG. 4; and
FIG. 7 is a fragmentary overhead plan view of an alternate embodiment of
the stress plate depicted in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIGS. 1-3, a stress plate incorporating the features of the
invention is shown and generally designated 10. The plate 10 is relatively
rigid, and is
made of either metal or plastic, as is well known in the art. In the pictured
embodiment,
the plate 10 is made of metal, is circular in shape and has a 3.0 inch
diameter, however
other shapes and sizes are contemplated including oval, square and triangular,
depending
on the application.
The plate 10 includes a main body 12 with an outer peripheral edge 14 and
at least one strengthening corrugation 1 G, pictured as an annular ring
stamped into the
surface of the main body 12, which is generally planar. The outer peripheral
edge 14 is
1 S vertically spaced from the main body 12 to define a declining outer rim.
In the preferred
embodiment, the corrugation 1 G may also be provided with three additional
radial rib
segments 18 which connect the corrugation 16 with the peripheral edge 14.
A generally conically-shaped depression 20 is preferably positioned
centrally on the main body 12, and is of sufficient depth to allow the top of
the head of
the fastener to be below the top of the rib on the plate. If other fasteners
are used, such
S
CA 02222820 1997-11-28
as those having flat heads, the flat head is preferably located on the main
body 12, and the
depression 20 is not required.
A generally centrally located opening or hole 22 is defined by the
depression 20 and is configured for receiving a fastener 24. In the preferred
embodiment,
the hole 22 is positioned on a central or vertical axis of both the depression
and the plate
10. The size or diameter of the hole 22 will vary with the application and the
size of the
fastener; however, in the preferred embodiment, the fastener 24 is a No. 12
size, and the
hole 22 is in the general range of 0.129 to 0.135 inch.
Referring now to FIG. 2, the fastener 24 is preferably a screw with a hex
head 26 at one end, a threaded portion 28 made up of a plurality of helical
threads 30, a
tip 32 opposite the head 26 and with the threaded portion 28 between the head
and tip,
and a shank 34 between the head and the threaded portion. In the preferred
embodiment,
the tip 32 is of a self tapping configuration and preferably is of the type
disclosed in
commonly assigned U.S. Patent No. 4,693,654, which is incorporated by
reference. In
the preferred embodiment, the threads 30 are in the modified buttress form,
and are coated
with an environmentally resistant protective coating. Furthermore, the
fasteners 24 may
be provided in any suitable length depending on the application. It is
contemplated that
the fasteners may fall within the range of 1.5 to 14 inches in length.
Suitable fasteners
are manufactured and sold by ITW Buildex, Itasca, Illinois, under the
trademark
HEXTRA.
6
CA 02222820 1997-11-28
Referring now to FIGs. 4-6, an important feature of the present stress plate
is that the hole 22 is angled relative to a vertical axis of the plate for
accommodating
the threads 30 of the fastener 24 so that, upon the engagement of the threads
30 in the
hole 22, the fastener is maintained in a generally perpendicular orientation
to the plane
S defined by the main body 12. In the preferred embodiment, the hole 22 is
disposed in the
depression 20 at an angle 8 to the vertical axis of the depression, and the
angle 8 is the
same as the angle of the threads, also known as the helix angle. By angling
the hole 22
in this manner, the fastener 24 is more tightly maintained in the hole, and is
also
maintained in a perpendicular orientation, which facilitates proper
installation. While the
10 exact angular orientation of the hole 22 will vary with the application and
the type of
fastener, in the preferred embodiment, the angle 8, which is also the helix
angle of the
screw, is in the range of 8°.
More specifically, the threads 30 are formed in a helix, while the hole 22
in the plate 10 is planar. Accordingly, on one side of the screw 24 the wall
of the hole 22
is nested, or positioned between the threads, and the inner diameter of the
plate abuts the
inner diameter, or root of the fastener. On the opposite side, the relative
angular
difference between the wall of the plate 10 and the thread is 2 times 0 and in
the opposite
direction, with respect to horizontal, and the thread cuts through the plate.
This cutting
of the plate 10 forces the screw 24 against the first side of the plate, thus
maintaining the
petpendicularity of the screw with respect to the plate.
7
CA 02222820 1997-11-28
Referring now to FIG. 4, the manner of manufacturing the plate 10 is
described in schematic detail. Initially, a hole punch 40 creates the hole 22
in the sheet
of metal l0a which will eventually become the plate 10. Next, a stamping die
42 having
a generally conical shape with an offset or angled base formation 44 creates
the angled
shape of the depression 20. Other portions of the die 42 (not shown) create
the
strengthening formations 16, 18 simultaneously with the creation of the
depression 20.
To achieve the desired perpendicular relationship between the fastener 24
and the hole 22, the angled base formation 44 is machined at the same angle 8
as is the
helix angle of the threads 30. Referring now to FIG. 6, a fragmentary side
view of the
plate 10 is depicted, and the angled nature of the opening 22 is seen. The
creation of the
opening 22 defines a first or long side 46 and a second or short side 48 of
the depression
20. It will be appreciated however, that the depression 20 and the opening 22
need not
be formed as shown. The short side 48 may be eliminated, and the "upper" end
of the
opening 22 shown on the right side of FIG. 4 may abut the planar main body 12,
and still
1 S achieve the desired helix angle of the opening 22.
Referring now to FIG. 5, a fragmentary enlarged side view of the threaded
portion 28 of the fastener 24 is shown. The fastener 24 has a root diameter R
and a wider
thread diameter T. Also, as described above, the threads 30 are oriented at a
helix angle
8, which is the same as the angle of orientation of the hole 22. In the
preferred
embodiment, when the fastener 24 is threadably engaged in the hole 22, one
side wall
between the short side 48, and the long side 46, will engage the outer
diameter T and the
8
CA 02222820 1997-11-28
other side wall will nest within the root diameter R. Through this engagement,
the
fastener 24 is maintained in a substantially vertical orientation, or
perpendicular relative
to the plane of the main body portion 12 of the plate 10.
Referring now to FIG. 7, an alternate embodiment of the stress plate 10 is
fragmentarily shown and is generally designated 50. With the exception of the
elements
described presently, the structure of the stress plate 50 is identical to the
plate 10 and is
not shown. The main distinguishing feature of the plate 50 is that a conical
depression
52 is at least partially defined by a series of annularly spaced tabs 54,
which create the
generally conical shape described above in relation to the depression 20.
As is the case with the plate 10, the plate 50 defines a central opening 56
which is angled at the same angle 8 as is the opening 22, and corresponds to
the helix
angle of the fastener 24. In the pictured embodiment, the opening 56 has a
diameter in
the range of 0.129 to 0.135 inch, which may vary with the application and type
of
fastener. Thus, ends of the tabs 54 define the opening 56. Further, an outer
diameter 58
of the depression 52 which defines the tabs 54 is in the preferred range of
0.220 to 0.225
inch, which also may vary with the application. The illustration of the plate
50 is
intended to establish that the depression 20, 52 need not be continuous in
construction to
achieve the goal of maintaining the fastener 24 in a substantially upright
position.
In operation, it is preferred that the fastener 24 and the plates 10, 50 be
assembled prior to shipment to the jobsite to reduce the amount of work
performed by the
installer, and to simplify the installation procedure. A suitable assembly of
fastener and
9
CA 02222820 1997-11-28
plate is indicated generally in FIG. 2 and designated 60. The installer then
carries a
plurality of the assemblies 60 in a suitable container to the jobsite, places
the individual
assemblies in their appropriate locations on the roof and proceeds to drive
the fasteners
into the roof using a driver tool as is well known in the art. The advantage
of the present
stress plate 10, 50 is that the fastener 24 is maintained in a generally
vertical position
relative to the plate so that the fastener is properly driven into the solid
base of the roof
deck to properly position the stress plate for the proper amount of fastening
power.
While various embodiments of the stress plate with angled hole of the
invention have been shown and described, it will be appreciated by those
skilled in the
art that changes and modifications may be made thereto without departing from
the
invention in its broader aspects and as set forth in the following claims.
